Rhode Island Department of Education Lesson Plan Lesson Title: Polar and Nonpolar Covalent Bonds State Standards:(GLEs/GSEs) GSE - PS1 (9-11) - 4 National Standards: Context of Lesson: This class will be after the lessons on molecular geometry. In this class the students will be introduced to the polarity of bonds. The students will learn that covalent bonds can be polar or nonpolar. Opportunities to Learn: Depth of Knowledge:
Level 1
Describe how electronegativities determine the distribution of charge in a polar molecule.
Label the positive and negative dipoles in a polar molecule.
Prerequisite Knowledge:
Periodic Table
Periodic Trends
Electronegativity
Covalent bonding
Plans for Differentiating Instruction: During this class the students will begin to see the differences in polar and nonpolar bonds. I will be doing a lot of lecturing; however, will be involving my students through questioning and giving them examples to do on their own. Accommodations and modifications: For the worksheets in the next class I would be able to modify the worksheet. I would modify the worksheet by taking out a few tricky questions that deal with dipole moments. Environmental factors: The students will be sitting in their normal groups. Materials:
Electronegativity chart
Periodic table
Magnets
Objectives:
The students will describe how electronegativities determine the distribution of charge in a polar molecule.
The students will label the positive and negative dipoles in a polar molecule.
Instruction: Opening:
We just learned about molecular geometry.
This gave us an insight into how molecules are shaped.
Do you remember the different molecular geometries?
What are they?
Can you think of an example?
I expect to hear water and ammonia.
Get the student to list the molecular geometries and examples.
Why is the molecular geometry or shape important?
Effects properties such as boiling/melting point.
In todays class we will take a look at covalent bonds that we have seen before but haven’t looked into as much.
Polar and nonpolar covalent bonds.
The example of water mentioned before will be studied a lot.
We learned that water is a bent molecule because of its two lone pairs. This is different from carbon dioxide which is linear.
Draw the difference.
Today we will learn about polarity which is a reason why water is essential for life. The polarity of water is responsible for several of the most important properties of water.
The shape of water (bent) allows for it to be polar.
Engagement:
Polarity is directly related to the elements electronegativity.
Does anyone remember what the term electronegativity means?
The ability of an atom to attract electrons when the atom is in a compound.
What does that mean?
Is there a trend in the periodic table?
Increase as we go across (left to right) the periodic table.
Decrease as we go down (top to bottom) the period table.
Why?
Valence electrons.
Elements with a lot of valence electrons are close to having an octet and therefore have a strong pull for electrons while electrons with few valence electrons have a tendency to give electrons away to form an octet.
Electronegativities are very important in polar and nonpolar bonds; they determine if a covalent bond is polar or nonpolar.
Polar and Nonpolar bonds.
Polar bonds have an uneven sharing of electrons while nonpolar bonds have an even sharing of electrons.
On page 237 in your book an analogy between polarity and a tug of war is used.
In a nonpolar bond each side of the rope has the same strength (3 people on each side) so the flag in the middle of the rope stays in the middle.
In a polar bond one side is stronger than the other (one extra person on one side) and the flag in the middle of the rope moves more towards one side (the more electronegative side.
What would the flag in the middle of the rope represent?
The electrons; in the polar bond example the flag moves closer to the stronger side (more electronegative because that side has a stronger attraction for the electrons).
Polar bond. (book says difference is 0.4-1.0 for moderately polar and 1.0-2.0 for very polar)
Uneven sharing of electrons.
Creates dipoles.
areas of opposite charge in molecules
illustrate how to draw them.
delta + and -
arrows
This will help to see if a molecule is polar or nonpolar.
Examples.
H2O, HF
Direction of dipole moment.
With the arrows and delta + and - we can see that in a polar bond one element has a higher density of electrons therefore is more negative.
When we talked about protons and electrons we talked about how opposite charges attract.
Knowing this, how would you expect a sample of HF to look like?
of water?
Give students some magnets to play around with.
The students will notice that the positive end of a magnet is attracted to the negative end and two like ends will repel each other. This should get the students to think about the alignment of atoms in a polar bond.
We can see that the delta + sides are attracted to the delta - sides creating weak attractions.
How would this effect a compounds properties? give a little while to think about it.
boiling and melting point
specific heat
surface tension
solubility
Also, because of the polarity we could see that polar molecules could align by charges in an electric field.
Draw
Nonpolar bond. (book says different is electronegativities is 0.0-0.4)
Even sharing of electrons.
diatomic molecules
Examples.
O2, N2, CH4
In symmetrical molecules you really need to draw the arrows because they represent the direction of the pull of electrons.
We know that the bond between a F and a C is polar.
The molecule that would form would be CF4 which is symmetric. If we draw this with arrows we see that each arrow is cancelled by another arrow so that this bond is not polar.
Draw molecule.
Closure:
Recap the days activities.
We reviewed electronegativity and related that directly to the new material of polarity.
What is the difference between polar and nonpolar bonds?
How does polarity effect the properties of a compound? Why?
Tomorrow we’re going to work on more examples of polar and nonpolar bonds. We will get more work on how to identify if a molecule is polar or nonpolar and learn how to use the electronegativity charts.
Assessment: I will assess my students with a worksheet on polarity that will be completed during tomorrows class. Reflections: (only done after lesson is enacted) Student Work Sample 1 – Approaching Proficiency: Student Work Sample 2 – Proficient: Student Work Sample 3 – Exceeds Proficiency:
Lesson Plan
Lesson Title: Polar and Nonpolar Covalent Bonds
State Standards: (GLEs/GSEs)
GSE - PS1 (9-11) - 4
National Standards:
Context of Lesson:
This class will be after the lessons on molecular geometry. In this class the students will be introduced to the polarity of bonds. The students will learn that covalent bonds can be polar or nonpolar.
Opportunities to Learn:
Depth of Knowledge:
Prerequisite Knowledge:
Plans for Differentiating Instruction:
During this class the students will begin to see the differences in polar and nonpolar bonds. I will be doing a lot of lecturing; however, will be involving my students through questioning and giving them examples to do on their own.
Accommodations and modifications:
For the worksheets in the next class I would be able to modify the worksheet. I would modify the worksheet by taking out a few tricky questions that deal with dipole moments.
Environmental factors:
The students will be sitting in their normal groups.
Materials:
Objectives:
Instruction:
Opening:
Engagement:
Closure:
Assessment:
I will assess my students with a worksheet on polarity that will be completed during tomorrows class.
Reflections:
(only done after lesson is enacted)
Student Work Sample 1 – Approaching Proficiency:
Student Work Sample 2 – Proficient:
Student Work Sample 3 – Exceeds Proficiency: